The present invention relates to a vehicle transmission gearshift.
Gear shifting of a vehicle transmission is effected by rotating a gear selector rod, which in turn rotates a drive dog for selectively engaging, according to its angular position, various shifting forks arranged about the gear selector rod and connected to the transmission gears. The selected gear is engaged by moving the selector rod axially, so as to drive the fork engaged by the drive dog in a predetermined direction, and so engage the transmission gear connected to the fork.
As rotation and axial displacement of the selector rod are normally controlled, via transmission means, by a gearshift lever (e.g. floor type) in the passenger compartment of the vehicle, engagement of the gear may occur before it is fully shifted, especially in the case of sporting type transmissions involving very little movement of the gearshift lever. As a result, the drive dog may engage (albeit partially) two adjacent forks simultaneously, thus simultaneously engaging two different speed gears and so damaging the transmission. Current solutions to the above problem consist in either avoiding too close an arrangement of the forks, thus increasing the size and reducing the response of the gearshift, or providing at least some of the gears with safety devices for preventing undesired engagement, U.S. Pat. Nos. 4,337,673 and 4,120,212, for example, relate to devices for preventing accidental engagement of the reverse gear. These, however, are relatively complex and cumbersome, and, as such, cannot be employed on all the gears.